[nmh-workers] config ? re Content-Disposition: attachment; ... filename=SOME_UTF-8_CODED_STRING

[nmh]

What's the (config file?) fix so the string in
  filename=SOME_UTF-8_CODED_STRING
associated w/below attachment headers
is properly decoded?

--
thanks!,
Tom
--
$ mhn -version
mhn -- nmh-1.7.1 built 2018-05-19 10:39:15 +0000 on epjdn.zq3q.org

--snip from troublesome email:
------=_Part_8269689_1936031958.1534387543169
Content-Type: application/pdf
Content-Transfer-Encoding: base64
Content-Disposition: attachment;
 filename="=?UTF-8?b?Y2xpbWF0ZSBmbHllciB1cGRhdGVkLnBkZg==?="
Content-ID: <address@hidden>
--snip